Omnidirectional antennae are multi-band capable as a result of the broadband nature thereof, and preferably radiate in vertical polarisation. When used in rail vehicles, such as locomotives or carriages, it is thus achieved that the vehicle can be linked for communication with a base station.
DE 103 59 605 A1 discloses an omnidirectional antenna which is attached inside buildings as an indoor antenna. The omnidirectional antenna comprises a monopole radiator which has a conical portion and is arranged at a distance above a baseplate or a counterweight surface. The monopole radiator is connected via the foot point thereof to the baseplate or the counterweight surface and is also held by means of an inner hood which encloses the monopole radiator. The inner hood is itself in turn enclosed by an outer hood.
A drawback of the antenna disclosed in DE 103 59 605 A1 is that the antenna is difficult to assemble and does not have sufficient resistance to vibrations such as may occur for example in rail vehicles. Among other things, these vibrations are due to vibrations caused by the drive device (for example a diesel engine) or due to laying gaps in the track itself, which make it possible for the track to expand at higher temperatures without deformation.
The example non-limiting technology herein provides a broadband omnidirectional antenna and a rail vehicle comprising an omnidirectional antenna of this kind which do not have the drawbacks of the prior art. The broadband omnidirectional antenna ought to be manufactured in a simpler manner, be able to permanently withstand the loads occurring when used in rail vehicles and be capable of very broadband operation.
The object is achieved for the broadband omnidirectional antenna, a corresponding rail vehicle, advantageous embodiments of the broadband omnidirectional antenna, and an advantageous embodiment of the rail vehicle.
The broadband omnidirectional antenna comprises a baseplate and a monopole radiator, which comprises a foot point and an end region, the end region being arranged opposite the foot point. The radiator extends along a longitudinal axis extending perpendicularly or predominantly perpendicularly to the baseplate. This means that the radiator extends away from, in other words rises from, the baseplate, the foot point thereof being arranged closer than the end region thereof to the baseplate. The radiator widens in cross section along the longitudinal axis thereof in at least a first portion located between the foot point thereof and the end region thereof, the walls of the radiator, which thus diverge, delimiting an accommodating chamber. The omnidirectional antenna further comprises at least one shell-shaped or trough-shaped holding and/or accommodating device. A holding and/or accommodating device inner contour is adapted at least over part of the periphery to an outer contour of the first portion of the radiator, resulting in at least part of at least the first portion of the radiator dipping into the holding and/or accommodating device and being held in particular form-fittingly thereby. The omnidirectional antenna also further comprises a holding means, the first end of which is fixed to the baseplate and the second end of which, opposite the first end, is fixed directly or indirectly to the radiator.
The use of the shell-shaped or trough-shaped holding and/or accommodating device, which may be funnel-shaped at least in a peripheral sub-region and serves as a centring aid for accommodating the radiator during assembly as well as permanently bracing said radiator after assembly is complete, is particularly advantageous. In this context, a large support surface of the radiator is form-fittingly positioned on the holding and/or accommodating device. This support surface is preferably several square centimeters, in particular more than 3 or more than 5 or more than 7 or more than 10 or more than 15 or more than 20 cm2. As a result, very high stability is achieved. To increase the stability further, the holding means is rigidly connected both to the baseplate and to the radiator itself. In this context, the baseplate is preferably connected to the rail vehicle via a screw connection. The omnidirectional antenna thus produced is very mechanically stable in construction and can also be manufactured in a very simple manner in terms of production. During final assembly, there are absolutely no solder connections, as is explained in greater detail below. At the same time, the electrical properties of the omnidirectional antenna are approximately constant over the entire service life.
As is already apparent from the term “omnidirectional”, the antenna radiates omnidirectionally. As a result of the achievable broadband nature, all the conventional frequency ranges, such as GSM, UMTS and LTE, can be covered. The antenna also operates in particular at upper boundary frequencies of over 2500 MHz or 3000 MHz or 3500 MHz or 4000 MHz or 4500 MHz or 5000 MHz or 5500 MHz. Preferably, it can be operated in a frequency range of from 697 MHz to 6000 MHz. In principle, use for lower and higher frequencies is also conceivable.
In a further embodiment, the omnidirectional antenna comprises a supporting and fixing portion, which is part of or is connected to the holding and/or accommodating device. The supporting and fixing portion is thus preferably fixed to an outer contour of the shell-shaped or trough-shaped holding and/or accommodating device via connecting elements. In this context, a support surface of the supporting and fixing portion is positioned on and/or screwed to the baseplate. This support surface extends preferably rectangularly away from the holding and/or accommodating device, in such a way that the centre of gravity of the support and fixing portion preferably does not coincide with the longitudinal axis which passes through the radiator and the holding and/or accommodating device. The support and fixing portion may also be referred to as a foot portion.
In an advantageous embodiment, the radiator comprises a second portion, the cross section remaining constant in the second portion. In this context, the second portion is either directly connected to the first portion or spaced apart from the first portion by a further portion. This does slightly increase the construction height of the omnidirectional antenna, but in return the bandwidth over which the omnidirectional antenna can be operated is greatly increased.
In a particularly advantageous embodiment, the height of the first portion and the height of the second portion vary along the longitudinal axis in the peripheral direction of the radiator. By way of the variation, the bandwidth of the omnidirectional antenna can be influenced. In this context, it is also possible for the radiator to have an asymmetrical cross section in the cross section thereof transverse to the longitudinal axis thereof. In this case, it could have a cross section in the shape of a part-circle in a first sub-region and one or more cross-sectional regions extending in a straight manner in another sub-region. In principle, it is thus possible for the radiator to be conical in one peripheral sub-region and cubic in other peripheral sub-regions. These two regions may even be formed simultaneously along a particular height, in other words along a length along the longitudinal axis. Preferably, the end region of the radiator is predominantly rectangular or square in a plan view.
Preferably, a bridge-like connecting portion is provided, which is arranged on the radiator or on the holding means and connects the radiator to the holding means and the holding means to the radiator. In this context, the connecting portion preferably extends, with a radial component, outwardly away from the radiator with respect to the longitudinal axis, or the connecting portion extends, with a radial component, in the direction of the radiator with respect to the longitudinal axis. In this context, the holding means is rigidly connected to the end of the connecting portion arranged furthest away from the radiator. Conversely, in the other embodiment the same applies to the radiator, which is thus rigidly connected to the end of the connecting portion furthest away from the holding means. The connecting portion is in particular arranged at the end region of the radiator. As a result, very high stability is achieved.
Preferably, the holding means is formed in a single piece together with the connecting portion and the radiator. This means that they consist of a common part and are preferably manufactured jointly by casting. In this context, the holding means is galvanically connected to the radiator. In principle, it would also be possible for the holding means and the radiator to consist of two separate parts, the connecting portion being part of either the holding means or the radiator. The holding means and the radiator are thus rigidly interconnected, in particular by a screw connection.
Advantageously, the radiator consists of metal or a metal alloy or comprises metal or a metal alloy. Alternatively, it could also consist of a dielectric, the outer face and/or inner face being provided with an electrically conductive layer. In the latter case, the radiator could be manufactured by plastics injection moulding. The same also applies to the holding means.
As a result of the use of the shell-shaped or trough-shaped holding and/or accommodating device, sufficient stability of the omnidirectional antenna is provided even if the omnidirectional antenna comprises exactly one holding means. This means that the radiator is electrically conductively connected, in a mechanically stable manner, to one point on the baseplate merely via the exactly one holding means. A holding means may also mean a column. In this context, the holding means is connected to the baseplate at exactly one point. As a result, manufacturing costs can be further reduced.
Advantageously, the omnidirectional antenna comprises a supply means for supplying the radiator at the foot point thereof. The supply means extends from the foot point in the direction of the baseplate. A plug element, preferably in the form of a socket (for example an N socket), is arranged on a lower face of the baseplate, which is opposite the mounting face having the accommodated radiator. A power cable, in particular in the form of a coaxial cable, can be connected to this plug element. On the lower face thereof, the baseplate preferably comprises an accommodating opening for the plug element. In relation thereto, the plug element preferably has an external thread which corresponds to an internal thread of the accommodating opening, in such a way that the plug element can be screwed into the accommodating opening of the baseplate. When the omnidirectional antenna is assembled, at least the first end of the supply means extends into the plug element, the first end of the supply means being designed to accommodate and electrically contact an internal conductor of the power cable. The first end of the supply means may be slotted in the longitudinal direction, resulting in a spring effect. As a result of this spring effect, reproducible electrical contact between the supply means and the internal conductor to be accommodated of the power cable can be achieved. In this context, the supply means is itself galvanically separated from the baseplate. Preferably, the supply means is connected to the radiator galvanically but without soldering, or alternatively it is capacitively coupled thereto.
In a further embodiment, the supply means comprises an external thread over a sub-length at the second end thereof. By means of this external thread, the supply means is or can be screwed into a corresponding internal thread at the foot point of the radiator, preferably with a defined torque, resulting in galvanic contact. If merely one capacitive coupling is desired, a dielectric, in particular in the form of a sleeve, may be arranged between the foot point of the radiator and the supply means. In a further embodiment, the sleeve may have an internal and an external thread, the external thread of the supply means being capable of being screwed into the internal thread of the dielectric sleeve. The external thread of the dielectric sleeve can in turn be mechanically connected to a corresponding internal thread at the foot point of the radiator. How far the supply means extends through the foot point into the accommodating space of the radiator may be adjusted as desired.
In a particularly advantageous embodiment, the omnidirectional antenna comprises a GNSS (global navigation satellite system) module. By means of a GNSS module of this type, the position of the omnidirectional antenna and thus of the rail vehicle can be determined. A GNSS module of this type may for example be GPS, GLONASS (global navigation satellite system), Galileo and/or Beidou. In this context, the GNSS module is arranged in the accommodating chamber of the radiator, in the end region thereof. As a result, the GNSS module is attached in a compact manner whilst stilling having good reception of the satellite navigation signals.
Preferably, when the omnidirectional antenna is assembled the GNSS module does not actually even extend past the end region of the radiator, and is thus located entirely within the antenna accommodating chamber.
So as to be able to fix the GNSS module sufficiently, in a further embodiment the radiator comprises at least one support shoulder (preferably a plurality of support shoulders) which extends from the inner face of the radiator, in other words starting from the inner contour of the radiator, into the accommodating chamber thereof. In this context, the GNSS module is positioned on the at least one support shoulder. This ensures that the position of the GNSS module does not change within the accommodating chamber, potentially impairing reception, even if vibrations occur.
In a preferred embodiment, the holding means comprises an accommodating groove, which is accessible from the outside and which extends over the entire length of the holding means and over the connecting portion, which is part of either the holding means or the radiator itself. In this case, this accommodating groove opens into the accommodating chamber of the radiator. As a result, a connection cable for powering the GNSS module can be introduced into the accommodating groove. This connection cable can be passed through the baseplate via a hole therein.
Also preferably, the omnidirectional antenna comprises a further cover hood, which is form-fittingly and/or frictionally connected to the baseplate and encloses both the radiator and the holding means and the holding and/or accommodating device, and prevents moisture from penetrating into the omnidirectional antenna. Also preferably, either the GNSS module may be screwed to the one or more support shoulders via one or more screw connections or a spring force which presses the module onto the support shoulders can be applied to the GNSS module by a spring element. A spring element of this type could be arranged between the hood and either the end region of the radiator or the GNSS module.
The rail vehicle is in particular a locomotive or a railway carriage. In this context, the rail vehicle is equipped with the broadband omnidirectional antenna. Preferably, the omnidirectional antenna is attached to the roof of the locomotive or motor trainset or of the railway carriage.
Preferably, the rail vehicle is driven electrically, drawing or being capable of drawing the electrical power from an overhead line. In this context, the holding means is selected or adjusted in terms of the diameter thereof and/or the electrical resistance thereof in such a way that the holding means can act as a fuse if the overhead line is released from the anchoring thereof and falls on the broadband antenna. In this case, a bolted short circuit would occur, and this could result in the control technology inside the train detecting the short circuit current and disconnecting the corresponding network segment. At the same time, the accommodating means connected to the radiator would be protected from damage.
Naturally, the omnidirectional antenna could also be installed on other vehicles, such as motor vehicles (for example cars or heavy goods vehicles) or ships or other means of transport such as underground trains or trams.